This invention relates generally to optical position location apparatuses for locating the position of an object along one or more coordinate axes and more specifically, it relates to a solid-state optical position determining apparatus for achieving such location.
Heretofore, there are known in the prior art several optical touch screen input apparatuses which have optically, or through a combination of mechanical and optical devices, been capable of determining the location of an object within a two dimensional target field. In particular, examples of such optical touch screen input devices are disclosed in U.S. Pat. No. 4,267,443 issued on May 12, 1981 to Carroll et al, and U.S. Pat. No. 4,420,261 issued on Dec. 13, 1983, to Barlow et al.
Further, there is disclosed in U.S. Pat. No. 4,553,842 entitled "Optical Position Determining Apparatus," which was issued on Nov. 19, 1985, and is assigned to the same assignee as this application, an optical position location apparatus for locating an object in two dimensions which includes a housing defining a target zone. The location of objects is to be determined within the target zone by detection of interruption of light paths dispersed across such target zone. In one corner of the housing, there are provided a light directing means, a mechanical scanner-detector assembly, and a light source. The scanner-detector assembly consists of a drive motor for rotating a detector housing containing a photo-detector. By rotating the detector housing with its associated aperture and lens, the photo-detector scans the target zone for the presence of returning light and produces an electrical signal in response to the presence of such light. However, this prior art location apparatus has the undesirable aspect of being susceptible to mechanical vibrations due to its use of a rotating detector housing, thereby affecting its reliability and accuracy in use. Further, this location apparatus suffers from the disadvantage of requiring large and heavyweight components occupying relatively large areas of space which increases cost in its manufacture and assembly.
It would therefore be desirable to provide an optical position determining apparatus which is formed completely of solid-state components and has a high degree of resistance to vibrations. The solid-state optical positioning determining apparatus of the present invention is, by its very design, efficient, low-cost, and reliable in nature. The present invention represents an improvement over U.S. Pat. No. 4,553,842, which is hereby incorporated by reference.